Unmanned aerial vehicles (UAVs) perform various tasks including aerial surveillance for military, civilian and commercial purposes.
U.S. Pat. No. 4,795,111 to Moller describes a vertical take-off and landing (VTOL) type of UAV that uses a single propeller to direct air through a single duct for generating lift. The single duct has multiple vanes and spoilers that act together to control the flight path of the UAV. At least the spoilers described in Moller are positioned within the single duct, which may reduce the air flow therethrough and the lift capabilities of this UAV. Furthermore, Moller describes an engine that requires a fuel tank, which is carried upon the UAV.
U.S. Pat. No. 5,152,478 to Cycon et al. describes another VTOL UAV with a single duct that is defined by a toroidal-shaped fuselage. This UAV has dual, counter-rotating blades that direct air through the single duct for generating lift. The flight path of the UAV is controlled by collective and cyclic pitch control of the counter-rotating blades. Cycon describes housing diametrically opposed fuel tanks within the toroidal-shaped fuselage.
U.S. Pat. No. 6,450,445 also to Moller describes another VTOL UAV that uses dual, counter-rotating blades that direct air through a single duct for generating lift. The flight path of the UAV is controlled by trough-shaped air deflection assemblies that are positioned at an output end of the duct for collecting and redirecting a portion of the directed air.
These known UAVs all require components such as fuel tanks or exposed deflection assemblies that contribute to the overall mass and size of the UAV.